Andrew Robert Buxton Cavendish, 11th Duke of Devonshire, KG, MC, PC, DL (2 January 1920 – 3 May 2004), styled Lord Andrew Cavendish until 1944 and Marquess of Hartington from 1944 to 1950, was a British Conservative and later Social Democratic Party politician. He was a minister in the government of Prime Minister Harold Macmillan (his uncle by marriage), but is best known for opening Chatsworth House to the public.

Cavendish served in the British Army during World War II. Having attended an Officer Cadet Training Unit, he was commissioned into the Coldstream Guards as a second lieutenant on 2 November 1940.[2] On 7 December 1944, while holding the rank of actingcaptain, he was awarded the Military Cross 'in recognition of gallant and distinguished services in Italy'.[3] The action took place on 27 July 1944 when his company was cut off for 36 hours in heavy combat near Strada, Italy. He held the rank of major at the end of the war.

The duke followed the family tradition of owning racehorses, the most famous of which was Park Top, the subject of the duke's first published book, A Romance of The Turf: Park Top, which was published in 1976. His autobiography, Accidents of Fortune, was published just before his death in 2004. The duke had many disputes over the years with the ramblers who used the paths near Chatsworth. Eventually though, in 1991, he signed an agreement with the Peak National Park Authority opening 1,300 acres (5 km²) of his estate to walkers. He said that everyone was "welcome in my back garden". The duke's real estate holdings were vast. In addition to Chatsworth he also owned Lismore Castle in Ireland and Bolton Abbey in North Yorkshire. He also owned the bookshop Heywood Hill and the gentleman's club Pratt's.

He was a major collector of contemporary British art, known especially for his patronage of Lucian Freud. He was one of the founders, and the chief patron of, the Next Century Foundation, in which capacity he hosted the private Chatsworth talks between representatives of the governments of the Arab World and Israel. The duke was listed at number 73 in the Sunday TimesSunday Times Rich List of the richest people in Great Britain in 2004.

Three of the couple's six children died soon after birth, and the Duke's extramarital affairs became public after he appeared as a witness at a burglary trial and was forced to admit, under oath, that he was on holiday with one of a series of younger women when the crime occurred at his London home. The Duke, however, claimed that much of his marriage's success was due to the Duchess's tolerance and broadmindedness. The Duchess, as chatelaine, was largely responsible for the success of Chatsworth as a commercial endeavour.[citation needed]

Cavendish's older brother William Cavendish, Marquess of Hartington, who would have inherited the dukedom, was killed in combat near the end of the war. With William's death, Andrew became heir and received the courtesy title of Marquess of Hartington, which he held from 1944 until 1950.

The 10th Duke died of a heart attack while visiting Eastbourne in November 1950 and Andrew, who was in Australia at the time, inherited the title.[7] The Duke died while being attended by suspected serial killerDr John Bodkin Adams, who was his doctor when visiting Eastbourne. No proper police investigation was ever conducted into the death but Cavendish later said "it should perhaps be noted that this doctor was not appointed to look after the health of my two younger sisters, who were then in their teens";[7] Adams had a reputation for grooming older patients to extract bequests.

Cavendish inherited the estate but also an inheritance tax bill of £7 million (£220 million in 2016), nearly 80 per cent of the value of the estate.[16][17] To meet this, the Duke had to sell off many art objects and antiques, including several Rembrandts, Van Dycks and Raffaello Santis, as well as thousands of acres of land.[17]

"Wonderful things have happened in my life — it's time my son had his turn. When I was young I used to like casinos, fast women and God knows what. Now my idea of Heaven, apart from being at Chatsworth, is to sit in the hall of Brooks's, having tea."

^Johnson, Frank (19 June 2004). "Notebook". The Telegraph. London. Retrieved 16 April 2011. [...] the three dukes among Ukip's patrons – Somerset, Rutland and the late Devonshire, as well as the Earl of Bradford and Lord Neidpath, heir to the earldom of Wemyss [...]